Summary of Significant Accounting Policies - Risk (Details) - Product	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Sales Revenue
Concentration of Risk
Percentage of consolidated total	100.00%	100.00%	100.00%
Sales Revenue | Gasoline and gasoline blendstocks
Concentration of Risk
Percentage of consolidated total	74.00%	65.00%	64.00%
Sales Revenue | Crude Oil And Crude Oil Logistics [Member]
Concentration of Risk
Percentage of consolidated total	1.00%	5.00%	7.00%
Sales Revenue | Distillates, Residual Oil, Natural Gas And Propane [Member]
Concentration of Risk
Percentage of consolidated total	22.00%	26.00%	24.00%
Sales Revenue | Station operations (convenience stores, rental and sundries)
Concentration of Risk
Percentage of consolidated total	3.00%	4.00%	5.00%
Product Margin [Member]
Concentration of Risk
Percentage of consolidated total	100.00%	100.00%	100.00%
Product Margin [Member] | Wholesale Segment
Concentration of Risk
Percentage of consolidated total	19.00%	23.00%	23.00%
Product Margin [Member] | Gasoline Distribution and Station Operations Segment
Concentration of Risk
Percentage of consolidated total	78.00%	74.00%	73.00%
Product Margin [Member] | Commercial Segment
Concentration of Risk
Percentage of consolidated total	3.00%	3.00%	4.00%